London is the capital and largest city of both England and the United Kingdom, with a population of around 8.8 million, and its metropolitan area is the largest in Western Europe, with a population of 14.9 million. It stands on the River Thames in south-east England at the head of a 50-mile (80 km) estuary down to the North Sea and has been a major settlement for nearly two millennia. The City of London, its ancient core and financial centre, was founded by the Romans as Londinium and retains its medieval boundaries. The City of Westminster, to the west of the City of London, has for centuries hosted the national government and parliament. In the 19th century, London grew rapidly, becoming the world's largest city at the time, as it expanded and absorbed the neighbouring county of Middlesex, and parts of Surrey and Kent. In 1965 it was combined with parts of Essex and Hertfordshire to create the administrative area of Greater London, which is governed by 33 local authorities and the Greater London Authority.

The City of Westminster is a city and borough in London. It is the site of the United Kingdom's Houses of Parliament and much of the British government. It occupies a large area of central London, including most of the West End. Many London landmarks are within the borough, including Buckingham Palace, Westminster Abbey, Whitehall, Westminster Cathedral, 10 Downing Street, and Trafalgar Square.